Animals experience:
a) only rem sleep during mating season.
b) sleep cycles in which rem sleep alternates with slow-wave nrem sleep.
c) global brain deactivation during sleep and do not dream.
d) only experience nrem sleep.

Option B, Sleep cycles in which REM sleep alternates with slow-wave NREM sleep.

Explanation:

The pattern of sleep is cyclical consisting of rapid eye movement (REM) pattern phase repeating itself after every ninety minutes. Within the gap of two REM phase, intermittent non rapid eye movement (NREM) pattern occurs. This type of sleep pattern is very usual in all mammals be it human or animals. During the REM phase of sleep, the brain is stimulated for its development and also protein production increases.  

While in NREM phase, some involuntary body movements such as eye twitching, body straightening etc occur.

Hence, option B is correct

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